Endpoint detection is a method adopted in semiconductor fabrication for detecting a completion of a process in order to stop the process on time. Various automated fabrication process may involve endpoint detection. For example, etching and/or deposition is known that an endpoint of an etching and/or deposition process may be determined by monitoring a level of emission of selected byproducts of the etching and/or deposition reaction. For example, an endpoint detector may be used for detecting byproducts of the etched and/or deposited layer in the exhaust stream of the etching chamber. The etching process is stopped when no more byproduct is detected.
Endpoint detection may also rely on light emitted by the plasma during the etching reaction. This light includes emissions at wavelengths representative of specific substances present in the plasma. Therefore, the level of a reaction byproduct may be monitored through measurement of emissions at the byproduct's particular emission wavelength. By monitoring the level of a byproduct which may originate from the layer being treated by plasma, the endpoint of the process is indicated by a sharp drop in the level of emitted reaction product. For example, in a plasma etching process wherein a layer of oxide is being removed, carbon monoxide (CO) is a typical byproduct released into the plasma. CO emits light at a wavelength of 483 nm. Therefore, when the oxide layer is fully removed, the CO emission decreases indicating the endpoint of the etch process.
However, the endpoint detection error is observed often time and sometime even causes wafer scrap because there is no endpoint being detected during a wafer patterning process. For the application on in situ chamber cleaning, the over or under etching due to the endpoint missing may either damage the chamber or leave residues falling on the wafers. Therefore, for these problems to be solved, relevant developments to advance the accuracy of detecting the endpoint are needed.